U.S. patent application number 15/767754 was filed with the patent office on 2018-10-25 for tangential joining method.
The applicant listed for this patent is TESA SE. Invention is credited to Klaus KEITE-TELGENBUSCHER, Christian SCHUH, Bjorn ZEYSING.
Application Number | 20180305586 15/767754 |
Document ID | / |
Family ID | 57113301 |
Filed Date | 2018-10-25 |
United States Patent
Application |
20180305586 |
Kind Code |
A1 |
SCHUH; Christian ; et
al. |
October 25, 2018 |
TANGENTIAL JOINING METHOD
Abstract
The invention relates to a joining method wherein a first
surface (2) of a first adherend (1) and a second surface (8) of a
second adherend (6) are bonded to one another by provision of an
adhesive tape (3) having a first side (4) and a second side (7),
there being disposed on the first side (4) a first activatable
adhesive and on the second side (7) a second activatable adhesive,
the latter being an activatable pressure-sensitive adhesive, the
first side (4) of the adhesive tape (3) is contacted with the first
surface (2) of the first adherend (1) to produce a preliminary
assembly, the second surface (8) of the second adherend (6) is
joined in a joining movement to the second side (7) of the adhesive
tape (3), the joining movement having a tangential component and a
perpendicular component relative to the second side (7) of the
adhesive tape (3), with a ratio between tangential and
perpendicular components of greater than 0.5, where a region of
contact between second surface (8) of the second adherend (6) and
second side (7) of the adhesive tape (3) is provided with a
nonaqueous lubricant.
Inventors: |
SCHUH; Christian; (Hamburg,
DE) ; ZEYSING; Bjorn; (Hamburg, DE) ;
KEITE-TELGENBUSCHER; Klaus; (Hamburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TESA SE |
Norderstedt |
|
DE |
|
|
Family ID: |
57113301 |
Appl. No.: |
15/767754 |
Filed: |
October 18, 2016 |
PCT Filed: |
October 18, 2016 |
PCT NO: |
PCT/EP2016/074933 |
371 Date: |
April 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J 2463/00 20130101;
C09J 2301/414 20200801; C09J 5/06 20130101; C09J 2467/006 20130101;
C09J 5/02 20130101; C09J 2475/00 20130101; B62D 65/024 20130101;
C09J 2400/163 20130101; B62D 27/026 20130101; C09J 11/04 20130101;
C09J 7/381 20180101; C09J 2400/12 20130101; C09J 2409/00 20130101;
F16B 11/006 20130101; C09J 2495/00 20130101 |
International
Class: |
C09J 7/38 20060101
C09J007/38; C09J 5/02 20060101 C09J005/02; C09J 11/04 20060101
C09J011/04; B62D 27/02 20060101 B62D027/02; B62D 65/02 20060101
B62D065/02; F16B 11/00 20060101 F16B011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2015 |
DE |
10 2015 220 311.5 |
Claims
1. A joining method wherein a first surface of a first adherend and
a second surface of a second adherend are bonded to one another by
provision of an adhesive tape having a first side and a second
side, there being disposed on the first side a first activatable
adhesive and on the second side a second activatable adhesive, the
latter being an activatable pressure-sensitive adhesive, the first
side of the adhesive tape contacted with the first surface of the
first adherend to produce a preliminary assembly, the second
surface of the second adherend is joined in a joining movement to
the second side of the adhesive tape, the joining movement having a
tangential component and a perpendicular component relative to the
second side of the adhesive tape, with a ratio between tangential
and perpendicular components of greater than 0.5, wherein a region
of contact between second surface of the second adherend and second
side of the adhesive tape is provided with a nonaqueous lubricant
which at room temperature is in fluid form and whose dynamic
viscosity is at least 5 mPa s.
2. The joining method as claimed in claim 1, wherein the lubricant
is selected from the group consisting of oils, greases,
petrolatums, hotmelt lubricants, low molecular mass polymers,
plasticizers, liquid resins, reactive resins, polyols, fatty acids,
esters of fatty acids, and silicone oils.
3. A joining method wherein a first surface of a first adherend and
a second surface of a second adherend are bonded to one another by
provision of an adhesive tape having a first side and a second
side, there being disposed on the first side a first activatable
adhesive and on the second side a second activatable adhesive, the
latter being an activatable pressure-sensitive adhesive, the first
side of the adhesive tape is contacted with the first surface of
the first adherend to produce a preliminary assembly, the second
surface of the second adherend is joined in a joining movement to
the second side of the adhesive tape, the joining movement having a
tangential component and a perpendicular component relative to the
second side of the adhesive tape, with a ratio between tangential
and perpendicular components of greater than 0.5, wherein a region
of contact between second surface (8) of the second adherend and
second side of the adhesive tape is provided with a nonaqueous
lubricant which is selected from the group consisting of greases,
petrolatums, hotmelt lubricants, low molecular mass polymers,
plasticizers, reactive resins, polyols, fatty acids and esters of
fatty acids.
4. The joining method as claimed in claim 1, wherein the ratio
selected between tangential and perpendicular components of the
joining movement is greater than 1.
5. The joining method as claimed in claim 1, wherein the second
adhesive of the second side of the adhesive tape is activated.
6. The joining method as claimed in claim 1, wherein the first
activatable adhesive is applied to the first side of the adhesive
tape (3) and the second activatable adhesive is applied to the
second side, and the first activatable adhesive bonds more quickly
to an oil-coated first surface of the first adherend than does the
second activatable adhesive to the second surface of the second
adherend.
7. The joining method as claimed in claim 1, wherein the first and
second surfaces, respectively, of first and second adherends are
first coated with the lubricant and then bonded to one another.
8. The joining method as claimed in claim 1, wherein the second
activatable adhesive, applied to the second side of the adhesive
tape in a thickness of 200 .mu.m, exhibits a peel adhesion, on a
steel substrate coated with 1 g/m.sup.2 of oil at a removal speed
of 300 mm/min after one hour of storage at 23.degree. C. and a
relative atmospheric humidity of 50%, of less than 50%, of the peel
adhesion after 24 h of storage.
9. The joining method as claimed in claim 1, wherein the second
activatable adhesive comprises a base polymer and a reactive
resin.
10. The joining method as claimed in claim 9, wherein the base
polymer is an elastomer selected from the group consisting of
acrylate, methacrylate, polyurethane, natural rubber, synthetic
rubber, (iso)butyl rubbers, nitrile rubbers, butadiene rubbers,
ethylene-propylene-diene rubbers, styrene block copolymers with an
elastomer block composed of unsaturated or partly or fully
hydrogenated polydiene blocks, comprising polybutadiene,
polyisoprene, poly(iso)butylene or copolymers thereof, polyolefins,
fluoropolymers, silicones, polyamides, and polyhydroxyethers,
comprising phenoxy resins.
11. The joining method as claimed in claim 9, wherein the reactive
resin is a constituent for a polymer from the group consisting of
polyepoxides, polyesters, polyethers, polyurethanes, polymers based
on phenolic resins, on cresol or on novolac, polysulfides,
polysiloxanes, and acrylic polymers.
12. The joining method as claimed in claim 1, wherein the adhesive
tape comprises a carrier layer selected from the group consisting
of polyethylene, polypropylene, oriented polypropylene (OPP),
cyclic olefin copolymers (COC), polyvinyl chloride (PVC),
polyesters, polyethylene terephthalate (PET), polyethylene
naphthalate (PEN), ethylene-vinyl alcohol (EVOH), polyvinylidene
chloride (PVDC), polyvinylidene fluoride (PVDF), polyacrylonitrile
(PAN), polycarbonate (PC), polyamide (PA), polyethersulfone (PES),
and polyimide (PI).
13. The joining method as claimed in claim 1, wherein for the first
and/or second adhesive(s) an oil absorber is selected from the
group consisting of phyllosilicates, zeolites, silica, graphites,
lime, polymers, cellulose and its derivatives, aerogel,
polyurethane, polyolefins, acrylate-nitrile-alcohol polymers,
urethane-isocyanate-alcohol polymers, perlites, silk plants, peat,
straw, and rubber.
14. The joining method as claimed in claim 1, wherein the lubricant
is first applied to the second side of the adhesive tape, and the
second side of the adhesive tape is thereafter contacted with the
second surface of the second adherend; and/or the lubricant is
first applied to the second surface of the second adherend and is
thereafter contacted with the second side of the adhesive tape;
and/or the lubricant used has a boiling temperature under ambient
pressure of more than 120.degree. C.; and/or the lubricant used has
a dynamic viscosity of more than 100 mPa s at a measuring
temperature of 25.degree. C. and a shear rate of 1 s.sup.-1; and/or
the lubricant used has a static contact angle on the second
adhesive of less than or equal to 60.degree., measured as
23.degree. C. and 50% relative atmospheric humidity; and/or the
lubricant used has a dynamic viscosity of less than or equal to 10
Pa.
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. The joining method as claimed in claim 1, wherein a contact
angle of the lubricant on the first activatable adhesive is greater
than 30.degree. and/or the contact angle of the lubricant on the
second activatable adhesive is less than 30.degree.; and/or the
contact angles measured between a drop of the lubricant and the
first and second adhesives lying beneath the drop differ by at
least 10.degree..
21. (canceled)
22. The joining method as claimed in claim 1, wherein the lubricant
is selected from the group consisting of mineral oil, paraffinic
oil, naphthenic oil, synthetic oil, silicone oil, anticorrosion
oil, forming oil liquid tackifier resin and reactive resin.
23. The joining method as claimed in claim 22, wherein the
anticorrosion oil is selected from the group consisting of prelube,
hotmelt, and spot lubricant.
24. The joining method as claimed in claim 1, wherein the
activatable adhesives and the lubricant are selected from the
following combinations: activatable adhesives comprising epoxide
monomer and/or epoxy resin, with lubricants based on mineral and/or
synthetic oil, activatable adhesives comprising oil absorbers, with
lubricants based on mineral and/or synthetic oil, activatable
adhesives comprising natural or synthetic rubber, with lubricants
based on mineral and/or synthetic oil, activatable adhesives
comprising natural or synthetic rubber, with lubricants composed of
liquid resins based on hydrocarbons, activatable adhesives
comprising particulate oil absorbers, with lubricants based on
reactive resins or liquid resins, activatable adhesives comprising
at least a reactive resin, with a lubricant from the same chemical
group as the reactive resin.
25. The joining method as claimed in claim 1, wherein a lubricant
used comprises a component from the same chemical group also used
in formulating the second adhesive disposed on the second side, or
from the group of low molecular mass polymers, liquid resins,
reactive resins, and absorbers.
26. The joining method as claimed in claim 1, wherein the lubricant
is applied in an amount of between 0.1 and 10 g/m.sup.2.
Description
[0001] The invention relates to a joining method in accordance with
the preamble of claim 1.
[0002] In order for support structures to be produced in vehicle
bodies, especially in automotive engineering, it is common for
profiles to be nested with one another. What this means is that a
first profile has a milled or other recess, into which a second
profile, shaped correspondingly, is inserted or engaged. Together,
therefore, the two profiles form a part-shell of a support. The
support structure itself may be configured as an open profile or as
a hollow profile and may encompass both parts. The purpose of the
nesting is generally to stiffen or seal the overall structure. The
profiles used for these purposes may be made, for example, from
extruded alloy metal, or may have been shaped from sheet metal
blanks.
[0003] During the production of the nested arrangement, the
profiles are in many cases displaced in one another in such a way
that the connecting faces move at least partially tangentially to
one another. The connecting faces may be parts of the profile body
or may be shaped flanges, their key function being to connect the
profiles.
[0004] In the prior art, the profiles used for the nested
arrangement are welded to one another, generally, at the connecting
faces. The primary method employed in this case is that of stop
welding. Alternatively, the profiles may be joined to one another
by soldering, crimping, clinching or riveting. Combinations of the
methods are also used.
[0005] As well as the joining techniques referred to above,
adhesive bonds as well are increasingly in use for the joining of
profiles. The adhesive bonds not only increase the stiffness of the
connection but are also suitable, in particular, for the joining of
different materials. At other locations in the vehicle body, beads
of adhesive are used for sealing, for thermal and electrical
insulation, and for noise reduction. The separation of, say,
aluminum and steel in a jointed connection by means of the adhesive
ensures that no galvanic corrosion is developed at this
location.
[0006] Adhesives used for producing support structures are
activatable structural adhesives of high viscosity. These adhesives
are applied generally in the form of beads. During and/or after
activation, the adhesives cure usually through a chemical reaction.
Activation may be accomplished by a supply of heat or by moisture,
radiation--UV radiation, for example--exclusion of oxygen, or other
known mechanisms.
[0007] Where two or more profiles, as part of the shell
construction of vehicle bodies, for example, are nested in such a
way that there is a tangential movement of the connecting face
coated with beads of structural adhesive, the structural adhesive
is then shifted from its position and smeared in an uncontrolled
way. As a result, bonding reliability is no longer assured. The
relevant prior art is represented, for example, by the paper
Joining with adhesive tapes in car body manufacture, Alexander
Wieczorek, given at the conference Fugen im Karosseriebau [Joining
in vehicle body construction], Bad Nauheim Mar. 24-26, 2015.
[0008] Proposed herein is the use of adhesive tapes for the bonding
of vehicle bodywork components.
[0009] Also known are adhesive tapes which attain strengths
suitable for the production of support structures generally by
means of a physical or chemical curing process. The adhesive tapes
may or may not have pressure-sensitive adhesive tack. In that case
the adhesive tape generally has no additional carrier. Nontacky
adhesive tapes are generally first joined by means of heating to a
first profile, to produce a preliminary assembly. As the adhesive
tape has sufficient viscosity, the nesting procedure can be carried
out with no shifting of the adhesive geometry in spite of
tangential movement. After joining, further heating then initiates
a flow of the adhesive onto the second profile and also, where
appropriate, chemical curing. A disadvantage here is the high cost
and effort involved in producing the preliminary assembly.
[0010] In the case of tacky adhesive tapes, the preliminary
assembly can be produced simply through self-adhesiveness. In the
case of the tangential movement during the joining operation,
however, the adhesive tape attaches to the second profile, thus
hindering the joining procedure and disrupting the clean formation
of the adhesive seam. After joining has taken place, chemical
curing is then generally initiated by means of further heating or
the ingress of atmospheric moisture. In the paper referred to, the
use is proposed of a hybrid adhesive tape having a tacky side and a
nontacky side. A disadvantage of that embodiment is that the
adhesive tape inevitably has a complex, multilayer construction.
Moreover, the assembly between the adherend component and the
nontacky side comes about only after the system has been heated.
Before that, the assembly has no strength.
[0011] When joining pressure-sensitive adhesive tapes with
tangential movement, it is known practice to use water, with or
without a surfactant, as the lubricant. The water then slowly
diffuses out of the bonded joint, and so adhesion to the substrate
surfaces is developed. Where reactive adhesive tapes are used, of
the kind employed for producing support structures, however, this
has the disadvantage that a high level of moisture during the
curing reactions could prevent full curing. This is the case, for
example, with the widespread epoxy resin adhesives. The bond then
loses strength. In the case of moisture-curing adhesives, active
wetting during joining would trigger the curing reaction
prematurely on the surface of the adhesive tape, to the detriment
of the attachment of the adhesive to the profile surface. Moreover,
a high moisture content can lead to unwanted foaming of the
adhesive in the course of subsequent heating. It is possible, not
least, for the relatively high volume of water to lead to
corrosion.
[0012] It is an object of the invention, therefore, to provide a
joining method wherein two adherends can be bonded more easily by
means of a tacky adhesive tape with at least partial tangential
movement of the adherends. In this case the joining procedure with
at least partial tangential movement is to be carried out without
substantial deformation of the adhesive tape geometry or shifting
of the adhesive tape fixed beforehand.
[0013] It is also an objective of the present invention to provide
an adhesively bonded assembly having the advantages stated.
[0014] With regard to the method, the object is achieved in a first
aspect by means of a method as stated at the outset that has the
features of claim 1.
[0015] In a second aspect, the object is also achieved by a method
as stated at the outset that has the features of claim 3.
[0016] In accordance with the invention, two adherends are bonded
to one another by an adhesive tape. A first side of the adhesive
tape is first bonded to a first surface of a first adherend. On the
first side of the adhesive tape there is a first activatable
adhesive disposed. Disposed on the second side is a second
activatable adhesive, which is an activatable pressure-sensitive
adhesive. The first and second adhesives may be identical to or
different from one another. With preference the first adhesive is
likewise an activatable pressure-sensitive adhesive. First of all a
preliminary assembly is produced from the first adherend and the
adhesive tape. The preliminary assembly is then contacted by the
free second side of the adhesive tape, to which the second adhesive
is applied, with a second surface of a second adherend. This
"contacting" is accomplished by a joining movement which comprises
a tangential component and a perpendicular component in relation to
the second side of the adhesive tape, with the ratio between
tangential and perpendicular components, in relation in particular
to at least part of the second side of the adhesive tape, being
greater than 0.5, preferably greater than 1, more preferably
greater than 4.
[0017] At a ratio of more than 0.5, the tangential component of the
joining movement is already sufficiently large for significant
attachment of the second side of the pressure-sensitive adhesive to
the second adherend to take place, thus hindering the attainment of
the final position of the joining movement. At a ratio of more than
1, the tangential component is predominant; in a ratio of 4 and
upward, the movement is determined so greatly by the tangential
component that it is impossible to make use, for example, of pasty
adhesives (see Wieczorek loc. sit.), and so the method of the
invention can be used with particular advantage.
[0018] The ratio of the two components to one another may be very
large, if the joining movement takes place almost tangentially to
the second side of the adhesive tape. In extremis the joining
movement may also take place completely tangentially to the second
side of the adhesive tape.
[0019] In order to prevent displacement or deformation of the
adhesive tape between the first and second adherends, the region of
contact between the second surface of the second adherend and the
second side of the adhesive tape has a nonaqueous lubricant. As a
result of the nonaqueous lubricant, the tacky second side of the
adhesive tape, on first making contact with the second surface of
the second adherend, does not attach immediately to the second
surface, but is instead able to glide along it until it reaches an
end position of the first and second adherends relative to one
another.
[0020] In particular, the second side of the adhesive tape has a
tacky adhesive. The adhesive is shaped in a layer-like or sheetlike
way. The adhesive tape may consist of a single, homogeneous
adhesive, but it is also conceivable for the adhesive tape to have
a multilayer construction, having in particular an inner carrier
layer coated on either side with a respective adhesive.
[0021] It is preferred, however, for the adhesive tape to have a
single-layer construction and for the adhesive tape to consist of a
single-layer pressure-sensitive adhesive (PSA), preferably an
activatable PSA. As a result, the preliminary assembly can be
easily produced, and the adhesive tape is simple and inexpensive to
produce.
[0022] The thickness of the adhesive tape corresponds to the
thickness customary for adhesive tapes, in other words, for
instance, from 1 .mu.m to 5 mm. Preferred for structural adhesive
bonds in the automobile segment is a thickness of 50 .mu.m to 5 mm,
more particularly of 150 .mu.m to 2 mm. With large adhesive tape
thicknesses of 200 .mu.m to 5 mm, more particularly of 500 .mu.m to
5 mm, premature attachment of the second adhesive tape side to the
second adherend surface is particularly disadvantageous, since in
that case a positional error of the adhesive bond becomes
particularly large. Adhesive tapes in this thickness range,
therefore, are used preferably in the method of the invention.
[0023] The adhesive tape may have a single-layer or multilayer
construction. In the case of a multilayer construction of the
adhesive tape, there may also be further layers present, of the
kind well known to the person skilled in the art of adhesive tapes:
examples are further layers of adhesive or further carrier layers,
primer layers or release layers, or layers having specifically
physical functions, examples being layers with optical effect or
layers which promote or inhibit permeation, layers featuring
thermal or electrical conductivity, etc.
[0024] The adhesive tape is generally provided as a section of a
long adhesive tape. The adhesive tape may be provided, for example,
as a sheet or as a section of a roll, or, favorably, as a diecut.
The adhesive tape may have a simple coherent construction or else
there may be holes or openings made in the adhesive tape. The
adhesive tape may fully cover the surface bounded by its external
periphery, or indeed, if it has openings, may also cover only parts
thereof or leave parts free. The adhesive tape is substantially
larger in two dimensions than in a third dimension. In the first
two dimensions, however, it may well also be of approximately the
same size, thus having a circular, square or other external
sheetlike form.
[0025] In accordance with the invention, the second side is
provided with an activatable pressure-sensitive adhesive.
Favorably, the first and second sides of the adhesive tape are
provided with an activatable pressure-sensitive adhesive. In
specific embodiments, the first and second sides may also comprise
the same adhesive.
[0026] As activatable PSAs it is possible in principle to employ
all customary PSA systems with activated bonding. The activation is
generally accomplished by an input of energy, by means for example
of actinic radiation or heat or mechanical energy, such as
ultrasound or friction, for example. Use is also made, however, of
chemical activation by means, for example, of moisture or oxygen or
the absence thereof, or by other chemical activators, such as
peroxides, for example.
[0027] Heat-activatedly bonding PSAs can be classed fundamentally
into two categories: thermoplastic heat-activatedly bonding PSAs
(hotmelt PSAs) and reactive heat-activatedly bonding PSAs (reactive
PSAs). This classification also includes those PSAs which can be
assigned to both categories, namely reactive and simultaneously
thermoplastic heat-activatedly bonding PSAs (reactive hotmelt
PSAs). For the production of support structures from nested
profiles, the preference is for reactive PSAs.
[0028] Thermoplastic PSAs are based on polymers which on heating
undergo reversible softening and which solidify again in the course
of cooling. Thermoplastic PSAs which have emerged as being
advantageous are in particular those on the basis of acrylates, of
polyolefins and copolymers of polyolefins, and of acid-modified
derivatives thereof, of thermoplastic polyurethanes, of polyesters
and their copolymers, and also of block copolymers such as styrene
block copolymers.
[0029] "On the basis of", "based" or "based on" means presently
that the properties of the adhesive are determined at least greatly
by the fundamental properties of one component, referred to as the
base polymer, though without ruling out the additional influencing
of the base polymers through use of modifying auxiliaries or
adjuvants or of further components in the composition. In
particular this may mean that the fraction of the base polymer in
the overall mass of a thermoplastic PSA is more than 50 wt %.
[0030] In contrast, reactive heat-activatedly bonding PSAs include
reactive components as well as the base polymer. The reactive
components are also referred to as "reactive resins", in which, by
the heating procedure, a crosslinking process is initiated which
after ending of the crosslinking reaction ensures a permanent
stable connection.
[0031] The base polymers of such adhesives preferably comprise
elastic components, as for example synthetic nitrile rubbers,
polyurethanes, acrylates or styrene block copolymers. Elastic
components of these kinds give the heat-activatedly bonding
adhesive a particularly high dimensional stability even under
pressure, on account of its high flow viscosity. The fraction of
the base polymer in the overall mass of a reactive heat-activated
PSA may also be less than 50 wt %, but generally more than 10 wt
%.
[0032] Radiation-activatable PSAs are likewise based on reactive
components. The reactive components may include, for example,
polymers or reactive resins in which the irradiation initiates a
crosslinking process which on ending of the crosslinking reaction
ensures a permanent, stable connection. Adhesives of this kind
preferably also include elastic components, of the kind set out
above.
[0033] Radiation-activatable PSAs are to be distinguished from
radiation-crosslinked PSAs, in which the properties of
pressure-sensitive adhesiveness are set by means of radiation
crosslinking during the production of the adhesive tape. With
radiation-activatable PSAs, the radiative activation takes place at
application. Following radiative activation, the adhesive is
generally no longer tacky.
[0034] Activatable pressure-sensitive adhesive tapes also include
pressure-sensitive adhesive tapes assembled from two or more films
of adhesive, as disclosed in DE 10 2013 222739 A1.
[0035] They are activated by the contacting of the two or more
films of adhesive.
[0036] As reactive resins it is possible in principle to use all
reactive constituents which are known to the person skilled in the
art of PSAs or reactive adhesives and which form crosslinking
reactive constituents and/or macromolecule-forming reactive
constituents, of the kind described for example in Gerd Habenicht:
Kleben--Grundlagen, Technologien, Anwendungen ["Adhesive
bonding--Principles, technologies, applications"], 6th edition,
Springer, 2009. These by way of example are constituents which form
polyepoxides, polyesters, polyethers, polyurethanes, and also
polymers based on phenolic resin, on cresol, or on novolac, and
polysulfides, polysiloxanes (constructed preferably from
silane-terminated polymers (STP)) or acrylic polymers (acrylic,
methacrylic).
[0037] The fraction of the reactive resin in the overall mass of an
activatable PSA based on a selected reactive resin may also be less
than 50 wt %, but generally more than 10 wt %.
[0038] Elastomers which can be used are in principle all customary
elastomers in the PSA field, of the kind described in, for example,
the "Handbook of Pressure Sensitive Adhesive Technology" by Donatas
Satas (Satas & Associates, Warwick 1999).
[0039] These are, for example, elastomers based on acrylates and/or
methacrylates, polyurethanes, natural rubbers, synthetic rubbers
such as butyl, (iso)butyl, nitrile or butadiene and
ethylene-propylene-diene rubbers, styrene block copolymers with an
elastomer block composed of unsaturated or partly or fully
hydrogenated polydiene blocks (polybutadiene, polyisoprene,
poly(iso)butylene, copolymers of these, and other elastomer blocks
familiar to the skilled person), polyolefins, fluoropolymers and/or
silicones. Also known is the use of polyamides, particularly their
elastic copolymers (Pebax), or polyhydroxyethers (e.g., phenoxy
resins).
[0040] Where rubber or synthetic rubber or blends produced
therefrom are used as base material for the PSA, the natural rubber
may be selected in principle from all available grades such as, for
example, crepe, RSS, ADS, TSR or CV products, depending on the
required level of purity and of viscosity, and the synthetic rubber
or synthetic rubbers may be selected from the groups of randomly
copolymerized styrene-butadiene rubbers (SBR), butadiene rubbers
(BR), synthetic polyisoprenes (IR), butyl rubbers (IIR),
halogenated butyl rubbers (XIIR), acrylate rubbers (ACM) or
ethylene-vinyl acetate copolymers (EVA) and/or blends thereof.
[0041] The elastomer may be linear, branched, star-shaped or
grafted in structure, to give but a few examples, and may be
constructed as a homopolymer, a random copolymer, an alternating
copolymer, or block copolymers. The designation "random copolymer"
in the sense of this invention includes not only copolymers in
which the comonomers employed in the polymerization are
incorporated purely statistically, but also those in which there
are gradients in the comonomer composition and/or local
accumulations of individual varieties of comonomer in the polymer
chains. Individual polymer blocks may have a copolymer block
(randomly or alternating) construction.
[0042] As activatable adhesives which are nontacky, of the kind
which may be employed on the first side of the adhesive tape, it is
possible in principle for all customary activatedly bonding
adhesive systems to be employed. As for the activatable PSAs,
activation is generally accomplished by an input of energy, by
means of actinic radiation or heat, for example. Use is also made,
however, of chemical activation, by means for example of moisture
or oxygen or exclusion thereof, or of other chemical activators,
such as peroxides, for example.
[0043] The further description corresponds to that of the
activatable PSAs.
[0044] The activatable PSA and/or the activatable adhesive may also
be implemented in the form of an incompatible blend of at least two
activatable PSAs and/or activatable adhesives.
[0045] In the case of a multilayer construction, the adhesive tape
may also comprise a carrier material.
[0046] The carrier material encompasses all sheetlike structures,
examples being two-dimensionally extended films or film sections,
tapes of extended length and limited width, tape sections, diecuts
(in the form, for example, of edge surrounds or borders of an
(opto)electronic arrangement), multilayer arrangements, and the
like. For different applications it is possible to combine any of a
very wide variety of different carriers, such as films, woven and
nonwoven fabrics, and papers, for example, with different
adhesives.
[0047] As material for the carrier of the adhesive tape, preference
is given to using polymer films, film composites, or films or film
composites with organic and/or inorganic layers. These kinds of
films/film composites may consist of any common plastics used for
film production, with examples, but without limitation, including
the following:
[0048] polyethylene, polypropylene--more particularly the oriented
polypropylene (OPP) produced by monoaxial or biaxial drawing,
cyclic olefin copolymers (COC), polyvinyl chloride (PVC),
polyesters--especially polyethylene terephthalate (PET) and
polyethylene naphthalate (PEN), ethylene-vinyl alcohol (EVOH),
polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF),
polyacrylonitrile (PAN), polycarbonate (PC), polyamide (PA),
polyethersulfone (PES), or polyimide (PI).
[0049] The carrier may be a combination, moreover, with organic or
inorganic coatings or layers. This can be done by customary
techniques such as, for example, surface coating, printing, vapor
coating, sputtering, coextruding or laminating. Examples--though
without limitation--here include, for instance, oxides or nitrides
of silicon and of aluminum, indium-tin oxide (ITO), or sol-gel
coatings.
[0050] The joining method of the invention is preferably employed
in order to bond two oil-coated first and second surfaces of first
and second adherends to one another.
[0051] In body construction in the automobile industry, in
particular, the adherends take the form of metal bodywork panels
coated with oil. In one advantageous embodiment of the activatable
PSA, therefore, the PSA is furnished with at least one oil
absorber. The oil absorber absorbs the oil on contact of the
adhesive with the surface of the adherend, and the PSA is able to
develop a firm connection with the joining surface. Suitable oil
absorbers are in principle all oil absorbers known to the skilled
person, and may take the form of a particulate solid or a liquid.
Oil absorbers used are generally materials from the group of the
inorganic solids, the synthetic organic compounds, and the natural
organic compounds.
[0052] By "particles" are meant, in the sense of DIN 53206-1:
1972-08, primary particles, aggregates, and agglomerates of the oil
absorber or oil absorbers. The "particle size" refers to the
maximum extent of a particle. The particle size is determined
preferably by laser diffraction in accordance with ISO 13320 (the
dispersing step dispersing agglomerates but not aggregates),
although other methods known to the skilled person are also
suitable. The possible shapes of the particles are very
diverse--examples are spherical, rodlet-shaped, fibrous, or
platelet-shaped.
[0053] The oil absorber is preferably selected from the group
encompassing materials based on phyllosilicates, zeolites, silica,
graphites, lime, polymers, celluloses and their derivatives,
aerogels, polyurethanes, polyolefins, acrylate-nitrile-alcohol
polymers, urethane-isocyanate-alcohol polymers, perlites, silk
plants, peat, straw, and rubber.
[0054] The first side of the adhesive tape is contacted with the
first surface of the first adherend to produce a preliminary
assembly. The contacting encompasses the at least part-area
application of the first side of the activatable pressure-sensitive
adhesive tape to the first surface of the first adherend. During
this step the adhesive tape--where there is a PSA on the first side
of the adhesive tape--is generally not activated. The assembly
hence comes about only by virtue of the tacky properties of the
adhesive tape. It is, however, also conceivable for the activatable
pressure-sensitive adhesive tape to be activated even before or
during the contacting, for instance if the chemical reaction is
very slow and is not concluded by the time of the joining of the
second substrate. Where the first side of the adhesive tape bears
an activatable adhesive which is not tacky, in general at least the
activatable adhesive is activated on the first side. Alternatively,
the first surface of the first adherend can also be activated, if
it is of activatable design.
[0055] The contacting may be accomplished by any methods customary
in the application of adhesive tapes, such as by manual
application, rolling, rollers, or contactless methods such as
compressed-air application, for example.
[0056] The second side of the adhesive tape is joined to the second
surface of the second adherend in a joining movement. Joining faces
referred to are the second side of the adhesive tape already
applied, and the surface of the second adherend that comes to lie
on this side after joining. The surfaces are of substantially the
same size and of the same geometric form. The joining movement is
the generally linear movement, as for example the movement of the
preliminary assembly to the second adherend, or that of the second
adherend to the preliminary assembly, which leads the two joining
faces into a position where one overlies the other. The joining
movement can be broken down into a component perpendicular to the
second side of the adhesive tape, and a component tangential to the
second side of the adhesive tape, the two components being
perpendicular to one another. The ratio between tangential movement
and perpendicular movement is greater than 0.5, preferably greater
than 1, more preferably greater than 4.
[0057] In accordance with the invention, the region of contact
between the second joining face and the second side is provided
with a nonaqueous lubricant. The lubricant enables a sliding of the
surface of the second surface of the second adherend over the tacky
surface of the adhesive tape.
[0058] In the PSA field, the skilled person would not select a
lubricant that remains permanently in the PSA, since the lubricant
would adversely affect the adhesion or the cohesion of the PSA. In
the prior art, therefore, an evaporating liquid, such as water, for
example, which as far as possible is incompatible with the
adhesive, is selected, so that there is no dissolution of the
lubricant in the adhesive. In the case of an activatable adhesive,
however, an evaporating liquid would be a disadvantage, since
residues of the liquid can lead to unwanted foaming during the
activating step, particularly in the case of thermal
activation.
[0059] In the case of the method of the invention, therefore,
lubricants advantageously used are those which at ambient pressure
have a boiling temperature of more than 120.degree. C., more
particularly more than 150.degree. C., and very preferably more
than 200.degree. C.
[0060] Since the lubricant is advantageously not removed from the
bonded joint by evaporation, it is advantageous if it is compatible
with the adhesive, in particular on the second side of the adhesive
tape and/or on the material of the second substrate, preferably
with the adhesive, so that it can be absorbed by the adhesive,
through processes of diffusion, for example. As a result, the
lubricant is removed from the interface between the second adhesive
tape surface and the surface of the second substrate, hence
allowing an adhesive bond to be developed more effectively.
[0061] In order to facilitate a process of diffusion, and the
sliding, provision is made in accordance with the invention for the
lubricant to be a fluid at room temperature. Room temperature here
refers to a temperature of 15-30.degree. C., preferably of
25.degree. C.
[0062] The fluidity is expressed and described hereinbelow by the
dynamic viscosity. A fluid so designated is a compound having a
dynamic viscosity of less than 10.sup.8 Pa s.
[0063] The dynamic viscosity is determined in general according to
DIN 53019. The viscosity is measured in a cylinder-type rotational
viscometer having a standard geometry according to DIN 53019-1 at a
measuring temperature of 25.degree. C. and a shear rate of 1
s.sup.-1. Given that this method is unable to determine very high
viscosities, it is also usual to ascertain the (complex) viscosity
according to ISO 6721-10 at 25.degree. C. and a frequency of 1
rad/s.
[0064] The fluid is not restricted in the nature of its fluidity:
it may, for example, comprise newtonian, dilatant, pseudoplastic,
plastic (with Bingham or Casson fluidity), shear time-dependent,
thixotropic, or rheopectic liquids.
[0065] The lubricant in the method of the invention preferably has
a dynamic viscosity of less than or equal to 10 Pa s, measured
according to DIN 53019-1 at a measuring temperature of 25.degree.
C. and a shear rate of 1 s.sup.-1.
[0066] In order to form a lubricious film on at least one of the
joining faces, moreover, provision is made in accordance with the
first aspect of the invention for the lubricant to have a dynamic
viscosity of more than 5 mPa s as measured according to DIN 53019-1
at a measuring temperature of 25.degree. C. and a shear rate of 1
s.sup.-1. If the viscosity is lower, the risk exists of formation
of drops due to the surface tension of the lubricant. The lubricant
preferably has a dynamic viscosity of more than 100 mPa s.
[0067] To form an extremely coherent lubricious film on the surface
of the adhesive, effective wetting of the adhesive with the
lubricant is an advantage. In one embodiment of the method of the
invention, therefore, the lubricant used preferably has a static
contact angle, measured between a drop of the lubricant and the
second side of the adhesive tape, lying beneath the drop, of less
than or equal to 60.degree., measured at 23.degree. C. and 50%
relative atmospheric humidity by dropwise application of 4 .mu.l of
the lubricant. The contact angle is preferably less than or equal
to 40.degree., more preferably less than or equal to 15.degree.. A
low contact angle indicates effective wetting of the adhesive by
the lubricant.
[0068] In the formation of a lubricious film it is necessary to
prevent the lubricant being absorbed too early by the PSA or by the
substrate, with the consequent deterioration of the lubricating
effect. The lubricant must therefore on the one hand be compatible
with the adhesive on the second side, but on the other hand must be
only slowly absorbed by it. This is verified by a slow development
of the peel adhesion on a steel substrate coated with 1 g/m.sup.2
of the lubricant, at 23.degree. C. and at a relative atmospheric
humidity of 50%. Preferred accordingly is a combination of adhesive
and lubricant wherein the peel adhesion of the activatable PSA on
the second side of the adhesive tape on such a substrate, at a
removal speed of 300 mm/min, after one hour of storage, is not
higher than 30% of the peel adhesion after 24 h of storage.
[0069] In accordance with the compatibility with the adhesive, the
lubricant is selected with the idea that the lubricant first,
during the joining procedure with the second substrate, allows the
substrate to slide on the tacky second side of the adhesive tape,
but is then removed from the contact surface by diffusion.
[0070] Nonaqueous lubricants which can be used are all nonaqueous
lubricants or slip agents known to the skilled person, with the
exception of solid lubricants which are present as particles (e.g.,
graphite), and hence include oils, greases, petrolatums, hotmelt
lubricants, and mixtures thereof, for example.
[0071] As nonaqueous lubricants it is also, however, possible to
use liquid components, of the kind used in the formulation of
adhesive or surface coating materials, examples being low molecular
mass polymers, liquid resins (plasticizing resins) or reactive
resins. Also conceivable is the use of silicone oils, in the case
of silicone-based PSAs, for example. Also suitable are polyols,
such as glycerol, liquid hydrocarbons of relatively high molecular
mass, such as paraffins, plasticizers, such as phthalates, and also
fatty acids and esters thereof. Such fluids may in accordance with
the invention also be used as part of a mixture, solution, or
emulsion.
[0072] Particularly suitable lubricants are those from the
following group: oils, greases, petrolatums, hotmelt lubricants,
low molecular mass polymers, plasticizers, liquid resins, reactive
resins, polyols, fatty acids and their esters, and silicone
oils.
[0073] According to the second aspect of the invention, nonaqueous
lubricants selected and used according to the invention are those
from the following group: greases, petrolatums, hotmelt lubricants,
low molecular mass polymers, plasticizers, liquid resins, reactive
resins, polyols, and fatty acids and their esters.
[0074] The lubricant is preferably selected from the group of the
mineral oils or synthetic oils, since these are often used as a
component in PSAs and are therefore compatible with numerous
activatable PSAs.
[0075] More preferably the lubricant is selected from the group of
the liquid tackifier resins (liquid resins, plasticizing resins;
see Satas) and reactive resins, since such resins are often
included as peel adhesion reinforcers in PSAs and are therefore
likewise highly compatible.
[0076] For the joining of metallic substrates, such as of steel
profiles, for example, is it particularly preferred for the
lubricant to be selected from the group of anticorrosion oils and
forming oils. These oils have a high slag resistance, and therefore
remain substantially in the applied layer thickness on the adhesive
tape or the substrate. They are based in general on mineral oils,
synthetic oils, or polymers (e.g., waxes or else biogenic
polymers), and often contain additives. Such oils are available for
example from companies such as Quaker under the Ferrocoat.RTM.
brand, from Rhenus under the Rotanor.RTM. band, from Fuchs under
the Anticorit.RTM. brand, from Zeller & Gmehlin under the
Multidravv.RTM. brand, and from Wocklum under the Furochem.RTM.
brand.
[0077] With very particular preference the lubricants are selected
from the group of lubricants approved according to VDA 230-213
(test methods for the product classes of prelube, prelube 2,
hotmelt, and spot lubricant; German Automobile Industry Association
(VDA), Forming Lubricants Technical Group).
[0078] Automakers generally require coils, blanks, pressed parts
and drawn parts made from aluminum-coated and uncoated steel sheets
to be protected from corrosion as they come from the rolled mill,
and the products employed for these purposes have to have a series
of properties.
[0079] These products are required to protect the metal surfaces in
the as-supplied state, and also to protect the parts manufactured
therefrom, against corrosion for the prescribed time under the
relevant climatic conditions, and may not lead to operational
disruptions during application in the cold-rolling mill and in the
subsequent production steps among the individual automakers.
[0080] The test protocols compiled in VDA 230-213, and the minimum
requirements prescribed by the automakers identified therein in the
notes, serve for the development of the products identified in the
title of the VDA standard. Lubricants meeting these minimum
requirements are products of the preferred product class identified
above.
[0081] In this context, prelube is an anticorrosion oil based on
mineral oil, synthetic oil, or from renewable raw materials, with
heightened requirements (relative to anticorrosion oil) concerning
the deep-drawing and lubricating properties, for use as a finishing
oil on all presently known coated and uncoated metal sheets of
steel.
[0082] Hotmelts are lubricants which at room temperature
(20.degree. C.-22.degree. C.) form nonrunning, pasty, thin films
almost firm to the touch, based on mineral oil, synthetic oil, or
from renewable raw materials, with heightened requirements
concerning the deep-drawing and lubricating properties by
comparison with prelubes. These products must be suitable for use
as a concluding coating on all presently known substrates, i.e.,
uncoated or coated metal sheets of aluminum materials and
steel.
[0083] Spot lubricants are products based on mineral oil, synthetic
oil, or from renewable raw materials, with heightened requirements
concerning the deep-drawing and lubricating properties, and are to
be applied shortly before the forming operation only in the event
that the finishing oil applied at the roll mill proves not to be
sufficient for forming.
[0084] Approved lubricants are, for example, Rustilo S 40 and
Iloform 951HM from Castrol, Anticorit RP 4107 S, Anticorit PL
3802-39 S, Anticorit PL 39 SX, Renoform MCO 3802, Renoform MCO
3028, Anticorit PL 39 SX, Anticorit PL 3802-39 LV from Fuchs,
Platinol B 804 3 COW from Oest, AP 170, AP 168/14, AP 167/22, AP
221, AP 227, AP 228/2 from Pfinder, Ensis PL 1608 from Shell,
Wedolit N22-3 and Wedolit N 22 NV from Wilhelm Dietz, Hotmelt E1,
Multidraw PL 61, KTL N16, Drylube E1 from Zeller+Gmelin, and
Ferrocoat 6130 from Quaker. Preferred lubricants are those selected
from this group.
[0085] The amount of the lubricant applied to the surface of
adhesive tape or substrate is preferably between 0.1 and 10
g/m.sup.2, preferably between 0.5 and 5 g/m.sup.2. An amount lower
than 0.1 g/m.sup.2 harbors the risk of inadequate sliding, while an
amount higher than 10 g/m.sup.2 harbors the risk of a detrimental
effect on adhesive bonding.
[0086] The lubricant may be present on the second side of the
adhesive tape and/or on the second surface of the second
adherend.
[0087] The lubricant is advantageously on the second side of the
adhesive tape, since by this means it is necessary only to provide
precise wetting by lubricant of the surface which itself is tacky
and comes into contact with the second substrate.
[0088] With further advantage the lubricant is located on the
second side of the second adherend prior to bonding. This is
especially advantageous when the lubricant for the substrate
fulfills another function as well as the lubricating, such as the
function of corrosion control. In that case, in general, a greater
part of the substrate is wetted with the lubricant than is
necessary for the purpose of lubricating during joining.
[0089] The lubricant may be applied by any of the methods known to
the skilled person, hence for instance by coating, printing,
spraying or dipping.
[0090] The combination of lubricant and activatable PSA is
preferably selected such that the bond strength of a section of the
activatable PSA 200 .mu.m thick, following activation in a tensile
shear test at 23.degree. C. and a relative atmospheric humidity of
50% of the steel substrate coated with 1 g/m.sup.2 of the
lubricant, ata removal speed of 1 mm/min, is not more than 15%,
more preferably not more than 10%, lower than on a steel substrate
not coated with lubricant.
[0091] Preferred combinations are as follows: [0092] activatable
adhesives comprising epoxide monomer and/or epoxy resin, with
lubricants based on mineral and/or synthetic oil [0093] activatable
adhesives comprising oil absorbers, with lubricants based on
mineral and/or synthetic oil [0094] activatable adhesives
comprising natural or synthetic rubber, with lubricants based on
mineral and/or synthetic oil [0095] activatable adhesives
comprising natural or synthetic rubber, with lubricants composed of
liquid resins based on hydrocarbons [0096] activatable adhesives
comprising particulate oil absorbers, with lubricants based on
reactive resins or liquid resins [0097] activatable adhesives
comprising at least a reactive resin, with a lubricant from the
same chemical group as the reactive resin.
[0098] From the same chemical group here means that the lubricant
contains reactive groups which the reactive resin also contains,
examples being cyclic ethers, hydroxyl groups, carbonyl groups,
amines, and also vinyl or allyl groups.
[0099] The activatable, pressure-sensitive adhesive tape may also
comprise a plurality of layers of activatable PSAs. The latter may
be the same or different, and are preferably different. Preferably,
then, the first side of the adhesive tape comprises a layer of a
first activatable PSA, and the second side of the adhesive tape
comprises a layer of a second activatable PSA. The thickness of the
layers as well may be the same or different. With preference the
layers are of different thicknesses, since by varying the
thicknesses it is possible to variably adapt the adhesion
properties to different substrates, and the behavior with respect
to the lubricant.
[0100] The adhesives differ preferably in compatibility with the
lubricant. Hence it is preferred for the peel adhesion of a section
200 .mu.m thick of the first activatable PSA from the first side of
the adhesive tape, at 23.degree. C. and a relative atmospheric
humidity of 50%, on a steel substrate coated with 1 g/m.sup.2 of
oil, at a removal speed of 300 mm/min, after one hour of storage to
be higher than 50% of the peel adhesion after 24 h of storage.
[0101] The peel adhesion of a section 200 .mu.m thick of the second
activatable PSA on the second side of the adhesive tape, at
23.degree. C. and a relative atmospheric humidity of 50%, on a
steel substrate coated with 1 g/m.sup.2 of oil, at a removal speed
of 300 mm/min, after one hour of storage, is preferably less than
50%, more preferably less than 30%, of the peel adhesion after 24 h
of storage.
[0102] A large contact angle indicates low wettability with the
lubricant. In this application, this means that the lubricant wets
the adhesive surface only partially and therefore that adhesion to
the substrate comes about at the locations that have not been
wetted. It is therefore advantageous for the contact angle of the
lubricant on the first activatable PSA to be greater than
30.degree.. The contact angle of the lubricant on the second
activatable PSA is preferably less than 30.degree..
[0103] Overall it is preferable for the contact angle, measured
between a drop of the lubricant and the PSA lying beneath the drop,
to differ at least by 10.degree., preferably by more than
20.degree..
[0104] Where a lubricant from the group of the mineral oils or
synthetic oils is used and where the first and second substrates
are coated with the lubricant, combinations preferred per se in
each case, between first and second activatable PSAs, comprise
activatable PSAs on the basis of the polymers and reactive resins,
respectively, that are marked by crosses in table 1 below.
TABLE-US-00001 TABLE 1 First activatable pressure-sensitive
adhesive based on Reactive resins Silane- Polymers terminated
Synthetic Acrylate/ Acrylate/ Polyester/ Polyurethane polymers
Polyurethane rubber methacrylate Polyolefin Epoxy methacrylate
polyether polyurea (STP) Second Polymers activatable Polyurethane X
X X pressure- Synthetic X sensitive rubber adhesive Acrylate/ X X X
based on methacrylate Polyolefin X Reactive resins Epoxy X X
Acrylate/ X methacrylate Polyester/ X polyether Polyurethane/ X
polyurea Silane- X terminated polymers (STP)
[0105] The invention is described with reference to a number of
exemplary embodiments, and in this connection;
[0106] FIG. 1 shows a preliminary assembly with an adhesive tape
applied to a first surface of a first adherend,
[0107] FIG. 2 shows the preliminary assembly produced in FIG. 1,
which is applied in at least partially tangential movement to a
second surface of a second adherend,
[0108] FIG. 3 shows first and second adherends bonded with the
adhesive tape of the invention,
[0109] FIG. 4a shows a vectorial division of the joining movement
into a tangential component and a perpendicular component with
respect to a second surface of the adhesive tape,
[0110] FIG. 4b shows first and second adherends assembled by
joining.
[0111] The figures are not to scale. FIG. 1 shows a first adherend
1. This is an oil-coated metal panel of the kind used in bodywork
construction for automobiles. An adhesive tape 3 is stuck to a
first surface 2 of the first adherend 1. The adhesive tape 3 is
stuck to the first adherend 1 in a first method step. The adhesive
tape 3 has a first side 4 which is bonded on the first surface 2 of
the first adherend. The first side of the adhesive tape is coated
with a first activatable PSA. The association of adhesive tape 3
and first adherend 1 according to FIG. 1 is also referred to here
as the preliminary assembly. The composition of the first PSA is
preferably such that the oil present on the metal panel is absorbed
quickly or displaced during application and therefore establishes
an adhesive bond with the first adherend 1.
[0112] FIG. 2 shows a second method step. A second adherend 6 is
joined to the first adherend 1 in a joining movement which includes
a tangential movement component relative to the first adherend 1.
With regard to at least a region 5 of a second adhesive tape side 7
which is opposite the first adhesive tape side 4, the joining
movement includes a tangential movement component in the sense that
a second surface 8 of the second adherend 6 moves, as a result of
the joining movement with a tangential movement component, to the
second side 7 of the adhesive tape in the region 5.
[0113] The tangential component of the joining movement, and a
component thereof perpendicular to the second side 7 of the
adhesive tape 3 in the region 5, have a ratio of 0.5, preferably
1.0, more preferably of more than 4.
[0114] The second side 7 of the adhesive tape 3 is formed by a
second activatable PSA. The second surface 8 of the second adherend
6 is coated in accordance with the invention with a nonaqueous
lubricant. As a result of the effect of the lubricant, the second
surface 8 of the second adherend 6 slides along on the second side
7 of the adhesive tape 3, without the adhesive tape 3 slipping. The
second side 7 of the adhesive tape 3 therefore does not attach
immediately on first contact to the second surface 8 of the second
adherend 6.
[0115] FIG. 3 shows a third method step, in which the first and
second adherends 1, 6 and the adhesive tape 3 have reached their
final position relative to one another. In the position shown in
FIG. 3, the two PSAs are activated and produce a strong adhesive
bond of the first surface 2 of the first adherend 1 to the second
surface 8 of the second adhered 6. The composition of the second
PSA is preferably such that it absorbs the lubricant applied to the
second surface 8 of the second adherend 6, allowing a firm bonded
connection to be produced between the adherends 1 and 6 following
activation of the PSAs.
[0116] FIG. 4 shows in part a) two adherends 1 and 6, the adherend
1 having two adhesive tapes 3 stuck to it so as to produce a
preliminary assembly. The second surface 7 of the adhesive tapes 3
is furnished with a lubricant. The second adherend 6 is guided
toward the first adherend 1 with the joining movement 9. The
joining movement 9 may be broken down into a component 10
tangential to the second surface of an adhesive tape, and a
component 11 perpendicular thereto. The angle between the
tangential and vertical components 10 and 11 is 90.degree.. The
ratio between tangential and perpendicular components is greater
than 0.5 and here in particular greater than 4. As a result of the
joining movement and the subsequent adhesive bonding with
activation of the activatable PSA, the two profiles 1 and 6 are
nested, as shown in part b) of FIG. 4.
[0117] Table 1 shows initially preferred combinations of a first
activatable PSA and a second activatable PSA. The idea behind the
table is that of designing the first activatable PSA in such a way
that it adheres as quickly as possible to the oil-coated metal
sheet forming the first surface 2 of the first adherend 1; the
first activatable PSA is based, for example, on a polymer that is
based on synthetic rubber or polyolefins, while the reactive resin
selected is an epoxide.
[0118] The second activatable PSA is selected such that it attaches
only with a delay to the second surface 8 of the second adherend 6,
which is likewise an oil-coated metal sheet; the second PSA is
based preferably, for example, on a polyurethane or acrylate, while
the activatable part selected in turn is an epoxide. Every PSA is
based on a viscoelastic part and an activatable part, with the
viscoelastic part based on one of the abovementioned polymers and
the activatable part on a reactive resin in the sense of the
definition given at the outset for "based". Preference is given to
combining viscoelastic parts with viscoelastic parts, reactive
parts with reactive parts, or reactive parts with viscoelastic
parts in accordance with table 1.
[0119] This means that provided the reactive part of the first
adhesive comprises epoxy resin, the elastomer of the second
adhesive is selected preferably freely from the group indicated in
table 1, and also any resin from the stated group, with the
exception of epoxide, is preferred as a reactive resin of the
second adhesive,
[0120] or that
[0121] first adhesives based in the viscoelastic part on a
polyolefin or synthetic rubber are preferably combined with second
adhesives based on a polyurethane or acrylic polymer,
[0122] or that
[0123] first adhesives based in the viscoelastic part on a
polyolefin or synthetic rubber are preferably combined with second
adhesives whose reactive part is based on epoxy resin.
[0124] In experiments, activatable PSAs K1 to K4 were produced. The
activatable PSAs are based on the following raw materials:
[0125] Raw Materials Used
[0126] Base Polymers
TABLE-US-00002 Breon Nitrile butadiene rubber with an acrylonitrile
N41H80 fraction of 41% from Zeon Chemicals (London, UK) Desmomelt
Largely linear hydroxyl polyurethane. Desmomelt 530 is 530 a highly
crystalline, elastic polyurethane of very low thermoplasticity from
Bayer MaterialScience. The enthalpy of fusion as measured by DSC is
54.7 J/g. Poly bd R Hydroxyl-terminated polybutadiene from Cray 45
HTLO Valley with a molecular weight Mw of about 2800 g/mol and a
hydroxyl functionality of about 2.5 Polyvest Maleic
anhydride-functionalized polybutadiene MA 75 from Evonik with a
molecular weight Mw of about 3000 g/mol and an acid number of about
80 mg KOH/g Azalt Bitumen 50/70 (B65) from Total 50/70
[0127] Reactive Resins
TABLE-US-00003 Epikote Difunctional bisphenol A/epichlorohydrin
liquid 828 epoxide with a weight per epoxide of about 190 g/eq from
Momentive. Viscosity at 25.degree. C. of about 13 Pa s. PolyDis
Nitrile rubber-modified epoxy resin based on PD3611 bisphenol F
diglycidyl ether with an elastomer content of 40% and a weight per
epoxide of 550 g/eq from Schill + Seilacher "Struktol". Viscosity
at 25.degree. C. of 10 000 Pa s. PolyDis Nitrile rubber-modified
epoxy resin based on PD3691 bisphenol A diglycidyl ether with an
elastomer content of 5% and a weight per epoxide of 205 g/eq from
Schill + Seilacher "Struktol". Viscosity at 25.degree. C. of 300 Pa
s. Tactix Dicyclopentadiene-epoxy-novolac resin with a weight 556
per epoxide of 215-235 g/eq and a softening point of 53.degree. C.
from Huntsman.
[0128] Curing Agents
TABLE-US-00004 Dyhard Latent curing agent from AlzChem for epoxy
100S systems, consisting of micronized dicyandiamide in which 98%
of the particles are smaller than 10 .mu.m. Dyhard Latent uron
accelerator for epoxy systems, in which UR500 98% of the particles
are smaller than 10 .mu.m. Mahlschwefel Twice-refined soluble
elemental sulfur with a 80/90.degree. purity of at least 99.9% from
Avokal MBTS 2,2'-Dibenzothiazyl disulfide from Weber&Schaer
TEDA Triethylenediamine crystal from Trigon
(1,4-diazabicyclo[2.2.2]octane)
[0129] Fillers
TABLE-US-00005 Wei.beta.feinkalk Calcium oxide CL 90 - Q -90 from
Rheinkalk Talkum Pharma M Talc from Scheruhn, BET surface area
about 4.6 m.sup.2/g Printex 60 Furnace black, oil absorption No.
118, BET surface area about 115 m.sup.2/g
[0130] The table below shows the composition in parts by weight of
adhesives K1 to K4 on the basis of the raw materials identified
above:
[0131] Adhesives:
TABLE-US-00006 TABLE 2 Example: K1 K2 K3 K4 Parts Parts Parts Parts
by wt by wt by wt by wt Breon N41H80 20 20 Desmomelt 530 20 Epikote
828 80 PolyDis PD3611 65 30 PolyDis PD3691 15 10 Tactix 556 40
Dyhard 100S 5.56 2.49 3.51 Dyhard UR500 0.56 0.25 0.35 Poly bd R 45
HTLO 28 Polyvest MA 75 15.1 Azalt 50/70 15 Mahlschwefel
80/90.degree. 16 MBTS 1.5 Wei.beta.feinkalk 3 Talkum 15 Printex 60
6.1 TEDA 3
[0132] The activatable PSAs K1 to K4 were prepared in the
laboratory by dissolving the polymer in butanone at 23.degree. C.
Next the reactive resins were added. Subsequently the curing agent
was added with vigorous shearing by stirring.
[0133] To produce layers of adhesive, the various adhesives were
applied from a solution to a conventional liner (siliconized
polyester film) by means of a laboratory coating apparatus, and
were dried. The layer thickness of adhesive after drying was
200.+-.10 .mu.m. Drying took place in each case initially at RT for
ten minutes and for ten minutes at 105.degree. C. in a laboratory
drying cabinet. The dried layers of adhesive were each lined,
immediately after drying, with a second liner (siliconized
polyester film with lower release force) on the open side.
[0134] For K5, first of all two components were prepared: the A
component was prepared by mixing the raw materials indicated, apart
from the Polyvest MA75, in a planetary mixer or dissolver for two
hours. To obtain a bubble-free product, the mixture was degassed
during the final ten minutes of the mixing process by application
of a reduced pressure of less than 0.02 bar (15 torr). The result
in each case was a paste which can be processed further at room
temperature. The B component was the Polyvest MA75.
[0135] A and B components were mixed together on a 2-component
mixing system and immediately coated out on a customary coating
unit, onto a double-sided release paper, to give a pasty film 200
.mu.m in thickness. On subsequent passage through a heating tunnel,
crosslinking took place at 70.degree. C. to form the
pressure-sensitive adhesive layer.
[0136] Lubricants:
[0137] G1: Ferrocoat 6130 from Quaker, a paraffinic oil (CAS
64742-65-0) having a viscosity of about 150 mPa s
[0138] G2: Anticorit PL 3802-39S, prelube oil from Fuchs, based on
naphthenic oil (CAS 265-156-6) with a viscosity of about 300 mPa
s
[0139] G3: Wingtack 10 from Cary Valley, an aliphatic hydrocarbon
resin having a viscosity of about 30 Pa s
[0140] G4: Epikote 828 from Momentive, an epoxy resin based on the
diglycidyl ether of bisphenol A and having an epoxy equivalent of
about 190 g with a viscosity of about 13 Pa s.
[0141] G5: Uvacure 1500 from Cytec, a cycloaliphatic diepoxide
(3,4-epoxycyclohexane or methyl 3,4-epoxycyclohexylcarboxylate)
with a viscosity of about 275 mPa s.
[0142] G6: Demineralized water, viscosity about 1 mPa s
[0143] Lubricants G1 and G2 are oils typically used in the
production of automobiles, whereas lubricants G3, G4 and G5 are
composed primarily of constituents which are constituents of
(activatable) PSAs and are therefore easier for the PSA to absorb.
G3 is a nonreactive resin, whereas lubricants G4 and G5 comprise
reactive resins. As a comparative substance from the prior art,
water (G6) was selected.
[0144] Measurement Values:
TABLE-US-00007 TABLE 3 Example: K1 K2 K3 K4 Peel adhesion
instantaneous, 5.0 12.1 6.7 2.6 uncured (steel)/N cm.sup.-1 Peel
adhesion after 24 h, 4.2 4.5 2.8 2.1 uncured (steel with lubricant
G1)/N cm.sup.-1 Peel adhesion after 1 h, uncured 2.2 1.3 0.1 1.8
(steel with G1)/N cm.sup.-1 Dynamic shear test (steel)/MPa 13 12 31
12 Dynamic shear test (steel with 11 11 28 11 G1)/MPa Wetting
angle/.degree. G1 7 33 G2 13 30 G4 55 76 G5 41 51 G6 93 103
[0145] The peel adhesions shown in table 3 for the uncured adhesive
tapes were determined in analogy to ISO 29862 (method 3) at
23.degree. C. and 50% relative atmospheric humidity with a removal
speed of 300 mm/min and a peel angle of 180.degree.. The thickness
of the layer of adhesive was 200 .mu.m in each case. An etched PET
film 50 .mu.m thick was used as reinforcing film, and is obtainable
from Coveme (Italy).
[0146] The substrate used comprises steel plates in accordance with
the standard. In some cases these plates were coated with lubricant
in an amount of about 1 g/m.sup.2. The measuring strip was bonded
using a roll-on machine at a temperature of 23.degree. C. The
adhesive tapes were removed immediately after application or after
a storage time of one or 24 h, respectively. The measurement value
(in N/cm) was obtained as the mean value from three individual
measurements.
[0147] In the determination of the peel adhesion on oiled steel
substrates, a paraffinic oil with a viscosity of about 300 mPa s
was used (Ferrocoat 6130).
[0148] The dynamic shear value shown in table 3 was determined in a
tensile shear test. The parameter for the quality of the bonding
achieved was the bond strength determined for the various adhesive
tapes and lubricants on an assembly produced by the method of the
invention. For this purpose, the bond strength was determined
quantitatively in each case in a dynamic tensile shear test based
on DIN-EN 1465 at 23.degree. C. and 50% rh for a test speed of 1
mm/min (results in N/mm.sup.2=MPa).
[0149] The test rods used were made of steel and were cleaned with
acetone prior to bonding. The lubricant, where used, was applied by
immersion of the test rod into a solution of the lubricant to
transfer it to one of the test elements. The solutions were
adjusted so as to deposit a layer of about 1 g/m.sup.2 of the
lubricant. The layer thicknesses of the adhesive tapes were about
200 .mu.m in each case. After joining had taken place, the bonded
test elements were stored at 23.degree. C. for 24 hours and then
cured at 180.degree. C. for 30 minutes. The figure reported is the
mean value from three measurements.
[0150] The wetting angle shown in table 3 was determined by means
of another common test method. The static contact angle of the
lubricant was measured in a method based on DIN EN 828, the drop
volume selected here being about 4 .mu.l. The measurement was
undertaken at a temperature of 23.degree. C. The angle reported
here is the mean wetting angle from three measurements.
[0151] In accordance with the standard, the contact angle was
measured about 10 s after the end of metering.
[0152] Table 3 shows that the peel adhesion resulting from use of
the lubricant G1, for which the experiments were carried out, after
24 hours and after one hour, is consistently lower, but the
decrease is heavily dependent on the particular adhesive used. The
adhesives K1 and K4 absorb the oil comparatively quickly, and so
after an hour of storage the peel adhesion is higher than 50% of
the peel adhesion after 24 h of storage, whereas the adhesives K2
and K3 absorb the oil more slowly, so that the peel adhesion after
an hour of storage is not higher than 30% of the peel adhesion
after 24 h of storage. Preferably, therefore, the adhesives K1 or
K4 would be selected for the first side 4 of an adhesive tape 3 for
the bonding of two oiled metal sheets 1 and 6, whereas the
adhesives K2 or K3 would be selected for the second side 7 of the
adhesive tape 3. In spite of the slower development of the peel
adhesion in the case of the adhesives K2 and K3, the shear strength
achieved after activation, as in the case of the adhesives K1 and
K4, is only slightly affected by the lubricant, and in particular
the shear strength is reduced by not more than 15%, and even, in
the case of K2, K3 and K4, by less than 10%.
[0153] It is important to assess the lubricity of the various
lubricants G1 to G6 applied to the adhesives K1 to K4. In this
case, the experimental design selected was as follows:
[0154] To simulate the sliding in a tangential joining method,
sections of the layers of adhesive produced, measuring 25.times.25
mm.sup.2, were laminated by their first side to a clean steel plate
in the laboratory, at 23.degree. C. and 50% relative atmospheric
humidity. Immediately thereafter a second steel plate, coated with
about 2 g/m.sup.2 of the lubricant, was applied vertically to the
second side of the adhesive tape section, and pressed on with a
force of about 10 N for about 1 s. Immediately thereafter the steel
plates were moved manually in a tangential movement relative to one
another, in order to determine the lubricity. Sliding with little
application of force was assessed as very good (++); sliding with
little application of force but a breakaway torque was assessed as
good (+); sliding with moderate application of force and a higher
breakaway torque was evaluated as satisfactory (o); sliding with a
high application of force was assessed as adequate (-); and
sticking was assessed as very poor (--). Since lubricant G6 could
not be coated homogeneously onto the steel plate even with addition
of surfactant, a drop of the lubricant measuring about 0.1 ml was
applied to the second side of the adhesive. Through the pressing of
the second steel plate, which here is untreated, the lubricant drop
was distributed on the second adhesive tape surface.
[0155] The following table summarizes the result:
TABLE-US-00008 TABLE 4 G1 G2 G3 G4 G5 G6 K1 ++ ++ 0 + ++ -- K2 ++
++ 0 + ++ -- K3 ++ ++ 0 + ++ -- K4 + + 0 + ++ -- (Lubricity: ++
very easy, no breakaway torque, + easy, low breakaway torque, 0
moderate, higher breakaway torque, - high, -- sticking, no sliding
possible)
[0156] First of all it became clear as early as during sample
preparation that water is an unsuitable lubricant here, since it
cannot be distributed evenly either over the substrate or over the
second adhesive tape surface. Lubricants here advantageously were
those having a contact angle on the adhesive of less than
60.degree., since with these lubricants it was easier to produce a
homogeneous film. Likewise advantageous is the effect of a
viscosity above that of water (>5 mPa s), more particularly a
viscosity of above 100 mPa s. In the case of the experiment carried
out in the variant described, the water showed no lubricating
effects; it was pressed out of the bonded joint, and the adhesion
faces stuck to one another.
[0157] It is clear that the low-viscosity nonaqueous lubricants G1,
G2 and G5 exhibit outstanding lubricating properties. The
lubricants G3 and G4, with a viscosity of more than 10 Pa s,
exhibit good lubricating properties, but these properties set in
only after a breakaway torque, so placing them within the framework
of the invention. At the same time, using the example of G1, it was
demonstrated that the lubricant is very well tolerated by the
adhesives K1, K2 and K4 and that peel adhesions are developed after
just a short time. The lubricant is resorbed more quickly by the
adhesive K4, leading to relatively high peel adhesions after an
hour. However, this still has no adverse effect on the lubricity.
The lubricant is resorbed more slowly by the adhesive K3, but
likewise leads to only a slight loss of shear strength.
[0158] The difference in the resorption rate was utilized in the
bonding of a two-ply adhesive tape consisting of a layer of K3 and
a layer of K4. In analogy to the lubricity test, the first side of
the adhesive tape with the adhesive K4 was laminated onto a steel
plate, here furnished with 2 g/m.sup.2 of the lubricant G1, and the
laminated assembly was stored for a minute under aforementioned
laboratory conditions. The lubricity test was then carried on as
described above with the lubricant G1. In the case of the
tangential movement, there was very good sliding on the surface of
the adhesive K3, whereas the adhesive K4 already exhibited
sufficient sticking on the likewise oiled surface of the first
substrate, meaning that there was no shifting of the adhesive tape
section there.
LIST OF REFERENCE NUMERALS
[0159] 1 first adherend [0160] 2 first surface of the first
adherend [0161] 3 adhesive tape [0162] 4 first side of the adhesive
tape [0163] 5 region [0164] 6 second adherend [0165] 7 second side
of the adhesive tape [0166] 8 second surface of the second adherend
[0167] 9 joining movement [0168] 10 component of the joining
movement tangential to the second side of the adhesive tape [0169]
11 component of the joining movement perpendicular to the second
side of the adhesive tape
* * * * *